common / precommon differences of internals?

[cj011]

after reading a thread, i was curious as to what are the differences between the internals between common and precommon blocks. are the rods all the same length for a 2.2 regardless if old or newer type block? and why does it seem that the precommon blocks are not recommended for higher hp abuse?

[ShelbyGLHS592]

There isn't that much difference in the internals. The non turbo 2 non-common block engines had lighter rods. I believe all common block turbo motors had the turbo 2 style rods. The 1985 turbo rods are the strongest of the non-common blocks. All of the turbo 2 pistons are the same.

The common block is beefier than the non-common block. I've always heard that the non-common blocks tend to flex when making more than 250 horsepower. Of course, there are alot of people making more power than that with non-common blocks.

[cj011]

thanks

[OmniSRT4]

Quote:

Originally posted by cj011 after reading a thread, i was curious as to what are the differences between the internals between common and precommon blocks. are the rods all the same length for a 2.2 regardless if old or newer type block? and why does it seem that the precommon blocks are not recommended for higher hp abuse?

All the 2.2 rods can be swapped from any car to another, but the T2 2.2 rods are much stronger. The only other close one is the 85 rod which is very similar. It has a press fit wrist pin though, not floating like the T2 rods.

One thing that does NOT swap is cranks. The main difference internally between the 2 is in 89 when the CB cam out the crank got a larger snout.

Pre 89 cranks do not work in a CB and vice vera.

This is not a real problem is ther ewas a forged pre 89 crank also.

The real problem is "block flex". The pre CB doesnt have the ~13 pounds of extra material to aid in stiffening the block.

I am sure this problem could be solved if someone created a billet bedplate. (making the pre-CB's as good or better than stock CB's and if used on the CB's it would make them near indestructable)

This is the design the new 2.4 uses and it is quite a bit stronger tha the 2 bolt mains we use.